In gateway devices of IP base for telephone set system, there are various kinds, such as an analog telephone set, a digital multifunction telephone set, an analog line, an ISDN line, and an IP line. They are separate devices. In a case where a plurality of gateway devices is installed, it is necessary to give addresses to respective devices, resulting in complicatedness in management and maintenance. Furthermore, it is necessary to secure a space and a power supply for installing a plurality of devices. In addition, in a case where a power failure countermeasure is taken, it becomes necessary to take a countermeasure for respective devices.
The IP-based gateway device communicates with a private branch exchange (hereafter referred to as PBX), which manages gateway devices and controls calls, by TCP or UDP packet communication. Commands given and taken between the PBX and the gateway device are included in packets. In addition, an MAC address and a device number (hereafter referred to as EN (Equipment Number)) are included in the commands to specify a device.
For using the gateway device, it is necessary to conduct registration into the PBX. It is necessary to specify a device in the PBX. Therefore, the gateway device transmits a command for registration including a MAC (Media Access Control) address to the PBX. If the PBX can specify the device, the PBX notifies the gateway device of the EN. On and after the registration, a call control is exercised with the EN included in the command.
As for a technique relating to the present invention, there is a description of a high-speed LAN switching control method (abstract and claim 1) in PTL 1. A LAN switch has a management table stating a local MAC address, a global MAC address, and a connection port. A local MAC address corresponding to a global MAC address is assigned to each terminal. The local MAC address is formed by compressing the global MAC address to the number of bits that can be given to a maximum number of terminals in a system to make them distinguishable. If a packet directed to a local MAC address is input, exchange connection to a corresponding stored connection port is conducted. The packet is transferred to a corresponding global MAC address.
In a communication system described in PTL 2, a single station side communication device connected to a network to which a plurality of multicast delivery servers are connected and one or more subscriber termination devices accommodating terminal devices are connected via an optical transmission medium. In PTL 2, there is a statement that a global IP address is rewritten to a local IP address on the basis of the global IP address and a source IP address in a multicast frame delivered by a multicast delivery server, in the communication system (abstract and claim 1). In PTL 2, there is a statement that a destination MAC address in a multicast frame is rewritten to a MAC address generated in relation to the local IP address (claim 2).